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Bombing resembles roadside incidents in war.

What happened at the Boston Marathon was inconceivable, horrific, shocking to most who have seen the videos and photos, but there are lots of Americans for whom the scene was appallingly familiar: veterans of the wars in Iraq and Afghanistan. I spoke to five men who served with my husband in the infantry. All of them went to Iraq at least once between 2006 and 2009 and are now scattered across the country, integrating into civilian life, more or less. They're my friends.

It wasn't like seeing the Iraq war break out on the Boston streets, they said, but they found their experiences rushing back while watching the news as they tried to figure out what kind of bomb it might have been. Because, for a year or more of their adult lives, what happened on Monday was a regular experience. Some worried the attack could become another pretense for war. Some tried to stifle a feeling that Americans don't care about the people overseas who are blown up all the time.

On Monday, T.J. Brummett came home from his construction job in Indiana and flipped on the TV just a few minutes after the explosion. He knew immediately it wasn't an accident. Brummett was an Army specialist deployed to Baghdad in 2006 and 2007, and for a few months, he was a driver for an Explosive Ordnance Disposal unit, or EOD, the guys who blow up bombs -- you probably saw them in The Hurt Locker. He was on call 24 hours a day, and "when someone was blown up, it was my job to get them there."

Brummett watched the news replaying the explosion over and over. "When C4 explodes it has a crack. It doesn't sound like anything else." The bombs in Boston didn't sound like that. This was more "gunpowderish," Brummett says. (The Washington Postreported Tuesday night that some investigators think black gunpowder might have been used because the blasts were not strong enough to cause structural damage to buildings or gouge the sidewalk.) "Probably had a timer," he said. (An official told The New York Times an egg timer was used.) Nick Cox, a former Army specialist who deployed to Iraq twice, saw the white smoke and figured it was the work of an "amateur." (Wired reports the white smoke indicates the explosive was gunpowder.) Of the bomb made of a pressure cooker, Staff Sgt. John Sellars thought, "Wow, that's some OIF-2 shit right there," referring to the military's term for the second year of combat operations in Iraq. "Ball-bearing IEDs would do a number on the old-school Humvees," Sellars said. "Then we started up-armoring everything… so that generation of IED wasn't any good anymore." In Iraq, the American armor and insurgents' weapons were constantly evolving. That hasn't happened in America, of course.